The present disclosure relates to a multi-beam laser cavity and a laser system comprising the cavity.
In the fields of maskless lithography and additive manufacturing it can be desired to provide an array of highly parallel laser sources, in which each channel can be controlled independently. The high degree of parallelism may provide a reduction of the beam size further down in the optical chain to meet the current state of the art values for common applications, e.g. writing conducting lines on flat panel displays with a few micrometers spot size.
For example, U.S. Pat. No. 8,488,638 describes a compact solid state laser that generates multiple wavelengths and multiple beams that are parallel, i.e., bore-sighted relative to each other. Each of the multiple laser beams can be at a different wavelength, pulse energy, pulse length, repetition rate and average power. Each of the laser beams can be turned on or off independently. The laser is comprised of an optically segmented gain section, common laser resonator with common surface segmented cavity mirrors, optically segmented pump laser, and different intra-cavity elements in each laser segment. Unfortunately, it can be difficult to generate and control multiple beams to have uniform beam properties.
For example, U.S. Pat. No. 6,222,577 describes direct patterning of a substrate by means of a solid state microchip laser, which is pumped by separate laser diodes and emits an array of laser spots. However, the laser system can be sensitive to small misalignment of the crystal facet. Furthermore, it can be difficult to control parameters like beam divergence and beam output size, e.g. because the size and divergence of the beams is strongly related to the heat deposited in the crystal, and therefore to the optical pump power.
U.S. Pat. No. 6,385,229 is directed to a laser having a resonator structure which efficiently generates only a fundamental transverse mode. The laser includes a laser source, first and second resonator mirrors, and an array illuminator optical system which is placed within the resonator optical system. The array illuminator optical system includes a Fourier plane array illuminator using one of a first lens array and a first phase grating; a Fourier transform lens; and a Fourier plane array illuminator using one of a second lens array and a second phase grating. The known laser system does not provide individual control of the laser beams.
There is a desire for a compact laser source array providing improved control and uniformity of the beam properties. There is a further desire for an array of highly parallel laser sources with individual control of the laser beams.